1. Field of the Invention
The present invention generally relates to automatic vehicle location systems. More particularly, the present invention relates to a reduction in the resource requirements for automatic vehicle location systems where the position of a large number of vehicles is frequently transmitted to a Dispatch Center.
2. Background
Automatic Vehicle Location (AVL) systems are used to keep track of a fleet of field vehicles for more efficient assignment of tasks in the field, monitoring productivity, and other reasons. Such systems typically have a Dispatch Center which receives a constant stream of position update messages that alert the Dispatch Center to any changes in the position of the vehicles. For example, each vehicle in the fleet sends a position update message to the Dispatch Center every 10 seconds.
Each field vehicle contains a mobile unit at least having an AVL box, a Mobile Data Terminal (MDT) usually in the form of a laptop or notebook computer, and a transceiver for broadcasting position update messages and for receiving information and instructions from the Dispatch Center.
The Dispatch Center of such a system includes a dispatch system, which stores logic and information (such as electronic maps) needed to receive and process position update messages from the fleet of field vehicles, and a transceiver for transmitting and receiving messages to and from the fleet of field vehicles.
A common use for an automatic vehicle location system is the tracking of public safety vehicles such as police cars, fire engines, paramedic vehicles and the like. In large municipalities with a great number of field vehicles to be monitored, the combination of a fixed bandwidth allocated for such services and the requirement that frequent position update messages be sent can cause "bottlenecks" and overwhelm the system, causing overall poor system performance.
There is a dire need to provide an AVL system with a lower bandwidth requirement for optimum system performance.